Re: [Openexr-devel] keycode

[Florian Kainz]

Hi Ken,

I think we should add something like this the struct you suggested to the
standard attributes, although I think "uint8_t" and "uint32_t" should be
replaced with "char" and "unsigned int"; those types are guaranteed to
have at least 8 and 32 bits respectively.  I would also suggest that we
get rid of the "reserved" field.

A couple of questions:

  * Is there a SMPTE keycode standard, other than the DPX specification?

  * Should slateInfo really be a field in the key code?  Somehow this feels
    more like a separate attribute.

  * In C++, having a default constructor for the keycode information would
    be useful.  Do you have suggestions for suitable default values for
    the fields in the struct?

Florian


Ken McGaugh wrote:
> Kevin Wheatley wrote:
>
> > Ken McGaugh wrote:
> >
> > > We want to store film keycode information in our exr's, and before I
> > > decide what header attribute(s) to create for this I wanted to
> > > know if anybody else is doing this already.  If so, what type and
> > > names did you choose for your header attributes.
> > >
> > > I was hoping to embed the keycode information into one string attribute
> > > rather than 5 attributes of various types is is done in DPX/cineon 
> > > files.
> >
> >
> >
> > timecode ?
> > framerate ?
> > ...
> >
> > soon you'll end up with cut down DPX format that supports HDR and
> > compression ... with a decent reference implementation.
> >
> > That idea sounds silly, I mean who on earth would want such a thing
> > :-)
>
> I've been researching this a bit more, and I think you are right that we
> shouldn't limit ourselves.  So why don't we just use the data structures
> specified in the SMPTE DPX spec as the attributes themselves.  There would
> be one for motion picture information, and another for television 
> information.
>
> For example, the motion picture information attribute might look like this:
>
>   struct DPXMotionPictureInfo
>   {
>       uint8_t    filmMfgCode[2];
>       uint8_t    filmType[2];
>       uint8_t    perfOffset[2];
>       uint8_t    prefix[6];
>       uint8_t    count[4];
>       uint8_t    format[32];
>       uint32_t   framePosition;
>       uint32_t   sequenceLength;
>       uint32_t   heldCount;
>       float      frameRate;
>       float      shutterAngle;
>       uint8_t    frameID[32];
>       uint8_t    slateInfo[100];
>       uint8_t    reserved[56];
>   };
>
>   typedef TypedAttribute<DPXMotionPictureInfo> DPXMPAttribute;
>
> In the implementation, the static type name for the attribute could be 
> "dpxmp".
>
> Any opinions?  Should we push for it (or something like it) to be put into
> the "standard" attributes?

I think we should somethin